Help Design a community pedal (Shimmer - Reverb.)

[artifus]

Is there a way to "fake" or "Fudge" the octave effect that would be close enough for our needs of a mostly clean trailing reverb effect?

yes. search forum for cmos. 4046, 4017, 4040, 4077, etc.

[armdnrdy]

^.... Or just learn to program the FV-1

I'll follow your lead! 

[Ark Angel HFB]

^.... Or just learn to program the FV-1

I'll follow your lead! 

Honestly if the chip was closer to $10 than $20 it would be much more appealing... Still it is really flexible.

I suppose I need to learn to program at some point... but I wanted to do the shimmer effect with simple stuff that everyone could do easy...

Maybe a reverb into that the highs alone were separated and slightly modulated in some way would work for a shimmer effect.

[armdnrdy]

Maybe a reverb into that the highs alone were separated and slightly modulated in some way would work for a shimmer effect.

I had that same thought  but then I took a listen to the Shimverb on YouTube to refresh my memory to what "shimmer" sounded like.

If you want that effect....it's an octave or in some shimmer capable effects it's a fifth. IMO the octave sounds much better.

We can try mixing in modulation to see if it sounds good. We don't even have to build the whole effect. Those of us who have reverb builds can either breadboard the LFO section or build a small daughter board for test purposes.

[Ark Angel HFB]

Maybe a reverb into that the highs alone were separated and slightly modulated in some way would work for a shimmer effect.

I had that same thought   but then I took a listen to the Shimverb on YouTube to refresh my memory to what "shimmer" sounded like.

If you want that effect....it's an octave or in some shimmer capable effects it's a fifth. IMO the octave sounds much better.

We can try mixing in modulation to see if it sounds good. We don't even have to build the whole effect. Those of us who have reverb builds can either breadboard the LFO section or build a small daughter board for test purposes.

I completely agree with you on the octave sounding better than the fifth...

I'd like this project to be as cheap as possible so as many people as possible can build one. The FV-1 is a sure solution... but it cost as much on it's own as making a whole pedal does... which for a lot of people i a turn off. I don't care if this is pure analog ... I mean PT2399 are not analog but they are simple enough that for delays/modulations people can just jump in and try projects with them... I'd like to see if we can do something like that.

Octaves are just "relative hertz" right?

The money question is... "Is there a cheap way to cheat and have a chip double the hertz of whatever signal it is fed?"

By my understanding octaves are relative. As long as the chip doubles the hertz it would be moving the signal up one octave.

[Ark Angel HFB]

Ok @#%$ it here is my full tinfoil hat idea. I'm sure something is wrong with this idea but I'm not sure about what it is...

Would it be possible to use Fullwave, AND Negative full wave, Rectification to create an audio wave that did not have a distorted sound but was 1 octave higher.

Full-wave Rectify the signal... (This doubles the frequency which means it has been raised 1 octave like we want)...  Then split the signal... Negative Full-wave Rectify one of the two signals... Delay the Negative Wave signal a bit... Then blend it with the Positive wave signal to form a signal that was 1 octave higher, but not distorted sounding due to having both positive and negative wave forms.

The only problem with the above is that if the delay time of the Negative wave signal is fixed... certain frequencies will be out of phase as the negative and positive wave forms will sync up and cancel each other out.

Still I think the delay time could be tuned so that the canceled frequencies were not greatly missed. Plus the reverb being "in and out" of phase in certain areas could give the reverb a certain movement that might be really really nice.

Well... Did I go full retard or does this have a chance at working?

[Digital Larry]

Shimmer reverb on the FV-1's been done.

http://www.spinsemi.com/forum/viewtopic.php?t=144

I have been learning how to program this chip for about 6 months and all I can say is that it's an investment.  I don't know what background other people using this chip have, but I got my EE degree 30 years ago and it required some really aggressive cobweb dusting.  And I'm not done yet!

[Ark Angel HFB]

Shimmer reverb on the FV-1's been done.

http://www.spinsemi.com/forum/viewtopic.php?t=144

I have been learning how to program this chip for about 6 months and all I can say is that it's an investment.  I don't know what background other people using this chip have, but I got my EE degree 30 years ago and it required some really aggressive cobweb dusting.  And I'm not done yet!

Not to sound like a git but I was kinda hoping as a community we could find a way to do something similar to the shimmer effect without using a $20 chip... >_>.

Still.... it is good to know that there is a working option... even if it is really pricey.

[WaveshapeIllusions]

Use one of those multiplier ICs. They often get used in ring modulators. If you feed the same signal to both ports you should get an octave up.

[mth5044]

^.... Or just learn to program the FV-1

I'll follow your lead! 

I can't say I haven't tried already. It was way over my head at the time. I started over with PICAXE and it's going pretty well so far.

I only mentioned the FV-1 because I had always postulated that that's what all the Mooer pedals are based on as IIRC most, if not all, of their pedals are 3-knob effects that are not far from preprogrammed stuff offered by the SpinSemi dudes.

[Jdansti]

Ok @#%$ it here is my full tinfoil hat idea. I'm sure something is wrong with this idea but I'm not sure about what it is...

Would it be possible to use Fullwave, AND Negative full wave, Rectification to create an audio wave that did not have a distorted sound but was 1 octave higher.

Full-wave Rectify the signal... Then split it... Negative Full-wave Rectify one of the signals... Delay the Negative Wave signal a bit... Then blend it with the Positive wave signal to form a signal that was 1 octave higher, but not distorted sounding due to having both positive and negative wave forms.

The only problem with the above is that if the delay time of the Negative wave signal is fixed... certain frequencies will be out of phase as the negative and positive wave forms will sync up and cancel each other out.

Still I think the delay time could be tuned so that the canceled frequencies were not commonly played notes. Plus the reverb being "in and out" of phase in certain areas could give the reverb a certain movement that might be really really nice.

Well... Did I go full retard or does this have a chance at working?

I wonder if this would alter the frequency or the amplitude.

[Ark Angel HFB]

I wonder if this would alter the frequency or the amplitude.

My thoughts on it were...

Full wave rectification on an audio signal will double the frequency by turning the negative wave form into positive wave form. Doubling the frequency means the Pitch will be raised 1 octave.

The draw back is that the sound would become distorted sounding due to the lack of a negative wave form. (This would sound like really harsh asymmetrical diode clipping.. because it would be.)

The solution would be to add a negative wave form back to the positive to restore the wave to a more natural form.

However, if a "negative full-wave-rectified" signal was add right back in... the phase would be perfect 180^o to the positive and the two signals, like two perfectly crashing waves would completely cancel each other... leaving almost silence.

The solution is to delay the "negative-full-wave-rectified" signal just slightly so that for most of the fundamental frequencies of notes, the "negative full-wave-rectification" would be Peeking in the gap between the peeks of the "Positive full-wave-rectification".

compared to the first signal, our ears would hear the new signal as a true wave, with both positive and negative, that was at double the frequency... Meaning a non-distorted, 1 octave higher signal... Which as far as I can tell is exactly what we want.

[Keppy]

Use one of those multiplier ICs. They often get used in ring modulators. If you feed the same signal to both ports you should get an octave up.

I think this is WAY more promising than a FWR. In fact, you don't even need a multiplier IC, you can use a 13700 by running the input signal to the bias pin, though it's a bit noisy. The trick with turning these chips into multipliers is getting the nulling right to eliminate bleed of the two signals being multiplied, but bleed probably isn't a concern here.

Um, my workshop still isn't set up since my move, so I humbly request that someone else try this out.

Oh, and since that leaves the other half of the IC unused... How about two octaves?

[armdnrdy]

Can you draw up the idea you have?

I'll try anything three times! 

[samhay]

Use one of those multiplier ICs. They often get used in ring modulators. If you feed the same signal to both ports you should get an octave up.

I think this is WAY more promising than a FWR. In fact, you don't even need a multiplier IC, you can use a 13700 by running the input signal to the bias pin, though it's a bit noisy. The trick with turning these chips into multipliers is getting the nulling right to eliminate bleed of the two signals being multiplied, but bleed probably isn't a concern here.

Um, my workshop still isn't set up since my move, so I humbly request that someone else try this out.

Oh, and since that leaves the other half of the IC unused... How about two octaves?

I have tried using both OTAs and muiltiplier ICs (AD632) to do octave up. They work, but you still have horrible intermodulation distortion, so when playing multiple notes at once you gets a real mess. I think there is a reason why there is no popular DIY clean octave up - it can't be done analogue in a reasonable way. However, it might not matter in a reverb if everything gets smeared out enough, and in this case, I would use a simple precision rectifier, which you can do with a dual op-amp, a couple of diodes, and change.

[Ark Angel HFB]

I'm down for trying stuff if you guys will draw something up... Pic help the noobs... I mean I don't need the drawing... but...

T_T... ok I need the drawing I have no clue what the hell I'm doing.

[Keppy]

Based on this circuit from the LM13700 datasheet:


Here's a modified 9v version:


If it seems promising, values can be tinkered with. Raising R3 will increase the volume, reducing apparent hiss. There should be some headroom there as the datasheet circuit is intended for line-level devices. R7 can be adjusted to get 4.5v on the buffer output for max headroom. R8 isn't really needed on the breadboard, it's an antipop resistor I didn't think to remove (I modified a previous circuit drawing to save time, hence the odd component numbering). Good luck!

[Keppy]

Oh, and I forgot to mention that R21 controls the amount of modulation AND the gain of the effect. If it seems to be working, we'll change that to get a modulation control that doesn't affect the overall gain.

[Keppy]

For a full wave rectifier, pick one from this page:
http://sound.westhost.com/appnotes/an001.htm

Just keep in mind those schems assume a bipolar supply, so any ground arrows connected to the signal path should actually be connected to 4.5v.

[Ark Angel HFB]

Is the LM13600N at the being used as a buffer? If so then I'd stile need to split the signal and get a Phase inverter to give me a negative wave form to be mixed back in with the Positive.

So I'm looking for a "phase inverter" circuit and what walks it way into this project... Tubes... Tubes baby...

No but honestly what is a good way to invert the phase after it has been rectified?

From there I just need to find a way to delay the phase inverted signal 5ms to 10ms and I will have the 1 Octave higher non-distortion effect.